Earth's early life would be invisible to NASA's planet-hunting telescope

NASA's upcoming planet-hunting telescope may be unable to detect signs of life on distant worlds because Earth itself took about three billion years to produce enough oxygen to be visible from space. This means the telescope could be observing an inhabited planet without seeing any evidence of life, according to a report from Space Daily.

The finding affects the search for extraterrestrial life, as oxygen is considered a key biosignature—a chemical sign of life. If many planets follow Earth's timeline, they might host life for billions of years before oxygen accumulates to detectable levels. This could mean that NASA's telescope, designed to scan for such biosignatures, might miss inhabited worlds.

The telescope in question is the James Webb Space Telescope, set to launch in 2021. It will study the atmospheres of exoplanets for gases like oxygen and methane. However, Earth's history suggests that even a planet teeming with life might not show oxygen for most of its existence.

Earth's first life appeared about 3.5 billion years ago, but oxygen only became abundant around 2.4 billion years ago due to the Great Oxidation Event caused by cyanobacteria. Before that, Earth's atmosphere had no detectable oxygen, despite being inhabited.

This implies that NASA's telescope might need to look for other biosignatures, such as methane or combinations of gases, rather than relying solely on oxygen. The agency may also need to consider that many planets could be in a pre-oxygen phase of life, requiring longer observation times or different detection methods.